1. Field of the Invention
The invention relates to a method of prolonging the lifetime of a thermal bubble inkjet print head, and more particularly to a method of obtaining an available set of parameters for prolonging the lifetime of a thermal bubble inkjet print head by means of investigating the effects of various parameters.
2. Description of the Related Art
In present technologies, all commercial thermal-bubble-ink-jet printers employ a single energy pulse applied to a heater in a print head to generate a bubble on a heated surface of the heater. Thus, an ink drop is expelled onto a piece of paper by the heat driven bubble.
In FIG. 3, a time-dependent bubble volume by applying a single pulse to a conventional printer, for example, HP500 printers, is shown. It is seen that as applying a single pulse with a pulse voltage (PV) of about 18V and pulse width (PW) of about 3 .mu.s to a print head, for example, HP51626, a bubble starts to be generated at about 2 .mu.s. More specifically, when the pulse voltage is applied for the first two micro-seconds, some small bubbles are generated randomly and locally on the heater surface. The small bubble is then coalesced into a single bubble afterwards. This single bubble reaches a maximum value of volume at about 7 .mu.s to 8 .mu.s. The bubble vanishes away at about 16 .mu.s to 20 .mu.s.
In FIG. 2, a PV-PW critical curve for a single pulse bubble generation is shown. When PV is taken as 18V, PW has to be wider than 1.0 .mu.s to generate a bubble.
Once the single energy pulse is turned off, this heat driven bubble starts to collapse. The bubble shrinks from a maximum value of volume to vanish. During a very short time while the bubble is collapsing, an extremely high pressure is caused to damage the heater severely. Consequently, the lifetime of the print head is shortened.